The present invention relates to heating a geological formation for the extraction of hydrocarbons, which is a method of well stimulation. In particular, the present invention relates to an advantageous radio frequency (RF) applicator and method that can be used to heat a geological formation to extract heavy hydrocarbons.
As the world's standard crude oil reserves are depleted, and the continued demand for oil causes oil prices to rise, oil producers are attempting to process hydrocarbons from bituminous ore, oil sands, tar sands, oil shale, and heavy oil deposits. These materials are often found in naturally occurring mixtures of sand or clay. Because of the extremely high viscosity of bituminous ore, oil sands, oil shale, tar sands, and heavy oil, the drilling and refinement methods used in extracting standard crude oil are typically not available. Therefore, recovery of oil from these deposits requires heating to separate hydrocarbons from other geologic materials and to maintain hydrocarbons at temperatures at which they will flow.
Current technology heats the hydrocarbon formations through the use of steam and sometimes through the use of RF energy to heat or preheat the formation. Steam has been used to provide heat in-situ, such as through a steam assisted gravity drainage (SAGD) system. Steam enhanced oil recovery may not be suitable for permafrost regions due to surface melting, in stratified and thin pay reservoirs with rock layers, and where there is insufficient caprock. Well start up, for example, the initiation of the steam convection, may be slow and unreliable as conducted heating in hydrocarbon ores is slow. Radio frequency electromagnetic heating is known for speed and penetration so unlike steam, conducted heating to initiate convection may not be required.
A list of possibly relevant patents and literature follows:
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